Smart cards, which are about the size of a credit card or smaller and that have contact pads on their lower surfaces, contain memory chips that are read out or written into by smart card connectors. A common type of smart card connector has a card-receiving slot at its rear end, into which a card can be forwardly inserted, until the card is fully inserted and blade contacts engage the card pads. The connector is mounted on a circuit board, with the contacts having tails soldered to traces on the board. Most contacts carry signals, and usually one contact is a ground contact. At least one of the signal contacts is an I/O (input/output) contact that may carry signals to read circuitry that authorizes a transaction, and protection of that signal contact is especially important.
The blade contacts are usually arranged in two rows, including forward and rearward rows. The blade contacts of the rear row extend to the rear of the connector where their tails are soldered to circuit board traces. The rear blade contacts and rear traces are the closest to the card user. Smart card connectors that are used in public places, and especially when unattended, are subject to fraudulent attempts, such as to authorize a transaction. One type of fraud attempt involves inserting a conductor from a position at the rear of the card connector slot while a card lies in the slot (the connector will not operate unless it senses a fully inserted slot). This may involve fraudulently drilling a hole into the rear of the connector or of the circuit board to insert the conductor against the tail or circuit board trace of the I/O contact. It would be useful if a region about a signal tail and corresponding circuit board trace were protected from engagement with a conductor inserted by an unauthorized person, and especially from a voltage (above or below ground potential) that such conductor carried.